The development of optical switches, including fiber optic switches, has been a result of a need to avoid electrical power in certain control lines because electrical switches in such situations can, for example, cause explosions in an explosive atmosphere and shocks if in the presence of liquid. Many optical switches are known in the art. See, e.g., U.S. Pat. No. 3,999,074; U.S. Pat. No. 4,045,667; U.S. Pat. No. 4,315,147; U.S. Pat. No. 4,904,044; U.S. Pat. No. 4,704,656; U.S. Pat. No. 5,892,862; U.S. Pat. No. 5,046,806.
For some optical switches, for example those containing a mirror actuator, the coupling efficiency of the reflected light and, therefore, the effectiveness of the signal detection is sensitive to alignment problems. The mirror actuator mechanism typically locates the mirror surface parallel to and in very close proximity to the fiber face in order to maintain good efficiency. In systems in which there is a gap between an end of the fiber and the mirror, the surfaces of the fiber and mirror may be prone to contamination, which can lead to each of back scattering and contamination, which in turn can lead to loss of light and hence reduced efficiency. Back scattering at any of the other optical interfaces can create additional noise in the optical signal and require additional signal processing or detector compensation to accurately detect the state of the switch.
One way of reducing the effect of back-scattered light on detector performance is to use fluorescence, such as atomic or molecular fluorescence, to create an optical switch. The property of fluorescence is well known in the art. Generally, an electron of an elemental or molecular target absorbs incident electromagnetic energy, typically light photons (FIG. 10), which transfers the energy of the photon to the electron. This raises the electron one or more energy level. This higher energy level is usually unstable. As the electron returns to the ground state it emits a new photon that has less energy than the original photon, which means that it has a longer wavelength of light than the photon absorbed. For example, a blue high energy photon can cause a red fluorescent photon. This change in energy levels between the original photon, which can be called illumination or excitation light, and the emitted photon is a characteristic property of a given compound and is known as the Stoke""s shift (FIG. 11). As used herein, the term fluorescence also refers to two-photon and multi-photon excitation, quantum dots, which are about nanometer sized crystals made from materials such as cadmium selenide that when excited by higher energy light will emit light of lower energy. The wavelength emitted is determined by the size of the nanocrystal. A larger crystal produces longer wavelength light and a shorter crystal produces shorter wavelength light. These materials are commercially available from Quantum Dot Corporation of Hayward, Calif. These materials are known in the art, and other methods of accepting light of one wavelength or wavelength band and emitting light at a detectably different wavelength or wavelength band are also included herein.
There has been a need for multi-state optical switches that can provide multiple wavelength or color-based return signals from a single wavelength or wavelength band impulse signal, as well as for other functions provided by characteristics of fluorescence, either fluorescence alone or in combination with reflectance. The present invention provides these and other related advantages.
The present invention provides methods and apparatus that comprise optical switches that take advantage of fluorescence to enhance sensitivity, speed or effectiveness. In some embodiments, the present invention provides a target area comprising at least one target surface comprising a fluorophore-containing target material, wherein the target surface comprises at least a first target area that provides a first fluorescent response when illuminated by excitation light and a second target area that provides a second light response when illuminated; the second response can be either reflectance light or fluorescent light, or other desired light response. The excitation light can be optically guided to the target via an optical fiber or other optical light guide. The switch can detect the resulting fluorescent light emitted from the target, for example by collecting the light into an optical fiber or other optical light guide and optically guiding it to the detector. The detector, which in this embodiment can include an operably connected computer, spectrometer, spectrograph or other optical analyzer, measures at least one of the relative intensity or wavelength of the response from the target, such as the induced fluorescence emission of the first target area, then determines the presence or type of the fluorescence.
The excitation light can be UV light, blue light, green light or other energy able to induce fluorescence in the target fluorophore; typically, such excitation light will be referred to herein as blue light.
In one embodiment, actuating the switch causes an optical fiber or other light guide to move relative to the target areas or the targets to move relative to the optical fiber. (The present invention comprises multiple aspects, features and embodiments; such multiple aspects, features and embodiments can be combined and permuted in any desired manner unless otherwise clear from the context.) This introduces different target areas, at least one of which is fluorescent, into the optical path. By detecting the difference(s) between the target areas, the apparatus and methods determine the state of the switch. The apparatus can then report the result or initiate an action that the switch controls.
In one embodiment the present invention provides switches that provide an excitation energy, transmit the excitation energy to the target, collect the emanated response light from the target, and transmit the emanated response light through an optical detector system, which can be in a controller, that detects the ratio of the intensities or other difference of one or more wavelengths or wavelength bands of the emitted response. The present invention can be used in any device for which an optical switch may be advantageous, including for example cars, airplanes, motorcycles, boats, other vehicles, medical equipment such as surgical pencils and controllers, electronic devices such as computers, telephones, and e-commerce related devices, manufacturing apparatus such as devices in production lines, lathes and molds, and household appliances.
Another embodiment of the invention provides a fiber optic, or other light guide, switching system which includes an optical switch mechanism having a movable actuator and a light guide such as an optical fiber or liquid light guide coupled at an end of the light guide to the actuator wherein the light guide conducts light from a light source to the end of the light guide at the optical switch mechanism. One or both of the actuator and the target is movable relative to each other so as to direct the light emitted by the light guide from one target area to another, such as one fluorescence to another. In one embodiment, the differing fluorescent properties in the switch are provided by a film, further preferably a flexible film, whose surface is conditioned to provide at least two different fluorescent surfaces. The film or other target can be positioned such that an end surface of the actuator or light guide abuts the film throughout its movement from one position to another. A detector detects light emitted from the film or other target material and returned by a light guide, which may or may not be the same light guide as the illumination light guide. The detector determines from which target area, such as from which fluorescent material, the return light was emitted.
Alternatively, or additionally, the switch can contain one or more mirrors, lenses, beam splitters or other beam control devices that can direct the excitation and emission light from one target area to another, again such as from one fluorescent material to another, or direct the collection of the emission light such as the fluorescent light.
The film may have a fluorescent target area and a non-fluorescent target area. Alternatively, the film may have multiple fluorescent surfaces (and, if desired, one or more non-fluorescent surfaces) which emit fluorescence at detectably different wavelength regions or intensities. Another possibility comprises target areas comprising graduated strength or color, or both, of emission for use as continuously variable controllers. Such graduated areas can be continuous or comprise a plurality of detectably different steps, for example 5, 15, 25 or more. The detector may have at least one corresponding filter assisting the detection of the multiple switch states, or the information from the detector may be processed either in a detector or downstream and therefrom the characteristics of the response light can be determined.
In another embodiment, where the target surface comprises at least three different response areas, the switch provides at least three detection states. By wrapping the target surface around a drum or other rotating device such as a disc, wheel or a belt, or other device able to sequentially pass the target surface past a detector or the detector past the target surface, the switch can become a directional counter. For example, if the surface comprises red, yellow and green emitting fluorophores (or red and green and non-fluorescent), then the direction of the switch can be determined by whether the colors are being detected as: red-yellow-green, or green-yellow-red. The total number of passages of the colors can give a discernible number, which number can be increased or decreased as the colors are read. Preferably, the directional counter is operably connected to a electronic system, typically digital or analog, that counts the iterations.
An advantage of the flexible film abutting the end of the actuator or fiber, or other arrangement wherein the illumination provider abuts the target surface, is the lowered likelihood of misalignment. Because the flexible film conforms to the face of the fiber or actuator, it maintains the parallelism between film and fiber surfaces desirable to enhance high coupling efficiency. And, arranging the end of the fiber to abut the flexible film throughout its range of movement reduces the likelihood of contamination of the area between the fiber and film with fluids or air-borne particulate.
The light guide may be, for example, a single optical fiber, a liquid light guide or a group of fibers providing a single optical path to and from the switching actuator.
A directional coupler may be coupled to the light guide, for example to direct light returning from the optical switch mechanism to the detector. The detector may include a photo detector positioned to detect light emitted from, or otherwise emanating from, the film.
In a further embodiment, for example where the switch is used in a surgical pencil or other device that comprises a light source maintained outside the device, the switch may comprise an excitation light source, a coupler optical assembly to direct the excitation light into the device and collect the fluorescent emission from the device, a separator that separates the light emanating from the target(s) into particular wavelength regions to be detected (this separator can be used with other embodiments as well), and one or more detectors to detect these wavelengths. The switch can also further comprise a light source maintained within the device containing the switch, or within the confines of the switch itself.
In one embodiment the coupler optical assembly comprises a lens to collimate light from the excitation source. The light from the light source can be passed through a dichroic mirror oriented at an angle, for example 45 degrees, to the optical axis of light, which can be a collimated beam, and that passes the shorter wavelength light excitation light of the excitation source. The light passing through the dichroic mirror is then directed to the target, then back to the mirror where it is reflected to the detector. Alternatively, the dichroic mirror can pass the emanating light and reflect the illumination light, in which case the optical pathway will be appropriately altered to fit such arrangement.
In a further embodiment, for example where the switch is used in a surgical pencil or other device that comprises a light source maintained outside the device, the switch may comprise an excitation light source, an optical assembly to direct the excitation light into a connector that allows light to be introduced into the device and collect the fluorescent emission, a separator to separate the light emitted from the fluorescent target into particular wavelength regions to be detected and one or more detectors to detect these wavelengths.
In another embodiment of the invention the optical assembly within the coupler may comprise an arrangement of fibers or other light guides that conducts light from the illumination source to the target and collects light from the target and directs it to two or more optically filtered photo detectors.
It is possible to avoid the need for a directional coupler between the light source and the detectors by using a plurality of light fibers in, for example in a bundle, with only some coupled to the light source and others coupled to the detector(s). A gap can be generally provided between the mirror surface and the fibers, so that some off-axis rays can couple from one fiber to the other. Where the illumination fibers and the detection fibers can also contact the target surface, for example where the fluorescent light is detected after a delay, or where the illumination and detection light guides are disposed on opposite sides of the target material or surface and detect transmissive light or other non-reflectance light.
A dual fiber system can avoid the problems associated with gap contamination and other problems that attenuate the light by providing a transparent layer of selected thickness in front of the fluorescent surface. The flexible film may be transparent and of a selected thickness with a mirror coating on the back so that the film itself provides the requisite spacing without permitting the entry of contamination.
In a preferred embodiment the present invention provides controllers and surgical pencil assemblies, the surgical pencil assembly comprising: a handpiece, hand actuated switch, cable and connector incorporating an optical path including a proximal end and a distal end, the handpiece being configured to position the distal end of the optical path to the fluorescent target; a light emitter window proximate to the distal end to direct an illumination light to the fluorescent target and collect the emitted light from the target; a controller assembly coupled to the connector of the surgical pencil assembly at the proximal end comprising an optical or fiber optic light guide to receive emanating light conducted to the proximal end of the surgical pencil assembly from the fluorescent target by the surgical pencil assembly light guide and an optical system to conduct the emanating light along at least a portion of a light path to the detector assembly; a wavelength selection filter aligned with the collection light guide to be disposed in the light path, and the wavelength selection filter assembly selectively transmitting one or more desired wavelength bands of the emanating light.
In preferred embodiments that relate to this and other aspects of the present invention (which is so for other preferred embodiments unless a given aspect of the invention indicates that such embodiment does not apply to that aspect), the collection light guide transmits the emanating light to the controller, which controller can include a detector as described herein.
In further preferred embodiments, the controller further comprises a band pass filter maintained within the excitation light optical path, for example at the proximal or distal end of the excitation light optical path, and disposed between the excitation light emitter and the excitation light optical path, wherein the band pass filter transmits a selected wavelength band of light. The selected wavelength band can be a suitable wavelength of light able to induce fluorescence in the surgical pencil assembly fluorescent target.
In still further preferred embodiments, the illumination light transmitted to the target consists essentially of a selected wavelength band and the light collection system further comprises a long pass filter disposed in the light path, wherein the long pass filter blocks light having about the same wavelength as the selected wavelength band of illumination light and transmits other light. For example, the long pass filter can be disposed at the distal end of the light collection system and can block blue light if desired.
The wavelength selection filter assembly can be maintained upstream in the light path from the long pass filter or the long pass filter can be maintained upstream in the light path from the wavelength selection filter assembly, and the long pass filter can be maintained upstream from the collection light guide.
In other aspects the present invention provides surgical pencil assemblies, the surgical pencil assembly comprising: a body including a proximal end and a distal end, the body being configured to position the distal end of the optical path proximate to the fluorescent target, means for emitting an illumination light from a location of the body at least proximate to the distal end; means for collecting and conducting an emanating light from the fluorescent target along a light path to a controller assembly coupled to the connector of the surgical pencil assembly at the proximal end, the controller comprising an optical or fiber optic light guide to receive emanating light conducted to the proximal end of the surgical pencil assembly from the fluorescent target by the surgical pencil assembly light guide and an optical system to conduct the emanating light along at least a portion of a light path to the detector assembly; a wavelength selection filter aligned with the collection light guide to be disposed in the light path, the wavelength selection filter assembly selectively transmitting one or more desired wavelength bands of the emanating light.
In certain preferred embodiments, the target is illuminated by conducting the illumination light from a light source maintained at the proximal end of the surgical pencil assembly to a light emitter maintained at the distal end of the surgical pencil assembly switch via an illumination light guide and then emitting the illumination light to the fluorescent target.
In further preferred embodiments, the illumination light is transmitted through a band pass filter maintained at the distal or proximal end of the surgical pencil assembly, wherein the band pass filter transmits a selected wavelength band of light and blocks other light. The selected wavelength band can be light able to induce fluorescence in the fluorescent target.
In other preferred embodiments, the illumination light emitted from the light emitter consists essentially of a selected wavelength band and the light collection system further comprises a long pass filter disposed in the light path, wherein the long pass filter blocks light having about the same wavelength as the selected wavelength band and transmits other light.
In some preferred embodiments, the illumination light is conducted from a light source maintained at the proximal end of the surgical pencil assembly and the controller assembly to the light emitter at the distal end of the surgical pencil assembly via the illumination light guide, and wherein a band pass filter that transmits substantially only a desired wavelength region of excitation light is disposed at the distal end of the illumination light guide.
In other preferred embodiments, the controller assembly comprises a fixed lens that is matched to the numerical aperture of the light guide of the surgical pencil assembly. This lens collects collimated light from the illumination path and focuses and transmits it into the optical light guide at the proximal end of the surgical pencil assembly. It can also collect and collimate light emitted from the proximal end of the surgical pencil assembly light guide and delivers it into the optical path of the controller detector assembly. The emitted light being transmitted along the light path passes through optical transmissive and reflective filters that select and dispose the light toward the detectors.
In further aspects of the invention light from the excitation source can be coupled into a lens that collects and collimates the excitation light and delivers it into the optical filter assembly and then to the lens which couples the excitation light into the light guide of the surgical handpiece.
In other embodiments, relating to both surgical pencils and other switches as described herein, the optical switch can comprise a light source disposed at or near the target, such as a light emitting diode. The light from the diode then strikes the target surface, where it causes the desired response in the target material, such as fluorescence, and is then collected and analyzed as described elsewhere herein.
In still more aspects the present invention provides filter assemblies for a surgical pencil assembly to transmit the emission from the fluorescent target to a controller/detector, comprising: a casing including a distal end with a first opening to receive a proximal section of the surgical pencil assembly, and a transmission passage extending between the opening and the detector or detectors, the transmission passage being configured to transmit light along a light path from the distal end to the proximal end of the casing; a rotatable housing attached to the casing, the rotatable housing including a knob configured to be gripped by a user and a filter holder positioned in the casing, the filter holder having a plurality of windows; and, at least one filter received in one of the windows, the housing rotating within the casing to position the at least one filter in alignment with the light path for selectively configuring the controller for different devices or desired purposes.
In other preferred embodiments, the filter assembly further comprises a fixed lens that is matched to the numerical aperture of the light guide of the surgical pencil assembly. This lens collects and collimates light from the proximal end of the surgical pencil.
In a preferred embodiment, the switches can be used in an array. For example, a plurality of switches can be coupled to an array detector, or an array of detectors.